EP0257526A2 - Amplitudentzerrer - Google Patents

Amplitudentzerrer Download PDF

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Publication number
EP0257526A2
EP0257526A2 EP87111977A EP87111977A EP0257526A2 EP 0257526 A2 EP0257526 A2 EP 0257526A2 EP 87111977 A EP87111977 A EP 87111977A EP 87111977 A EP87111977 A EP 87111977A EP 0257526 A2 EP0257526 A2 EP 0257526A2
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EP
European Patent Office
Prior art keywords
circuit
amplitude
path
attenuator
minimum phase
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP87111977A
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English (en)
French (fr)
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EP0257526A3 (en
EP0257526B1 (de
Inventor
Toshiaki Suzuki
Akira Nishimura
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Fujitsu Ltd
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Fujitsu Ltd
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Filing date
Publication date
Priority claimed from JP61191636A external-priority patent/JPH06101696B2/ja
Priority claimed from JP30747086A external-priority patent/JPS63158921A/ja
Application filed by Fujitsu Ltd filed Critical Fujitsu Ltd
Publication of EP0257526A2 publication Critical patent/EP0257526A2/de
Publication of EP0257526A3 publication Critical patent/EP0257526A3/en
Application granted granted Critical
Publication of EP0257526B1 publication Critical patent/EP0257526B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising
    • H04B3/14—Control of transmission; Equalising characterised by the equalising network used
    • H04B3/143—Control of transmission; Equalising characterised by the equalising network used using amplitude-frequency equalisers
    • H04B3/145—Control of transmission; Equalising characterised by the equalising network used using amplitude-frequency equalisers variable equalisers

Definitions

  • the present invention relates to an amplitude equalizer, more particularly, to an amplitude equalizer able to produce an output having a flat delay-frequency characteristic and a powerful amplitude-frequency characteristic.
  • the amplitude equalizer of the present inven­tion is useful as an equalizer for equalizing, in particular, the first order slope in amplitude distortion due to the above-mentioned multi-path fading.
  • amplitude equalizers are those comprised of constant resistor networks using only passive elements such as capacitors (C), induc­tors (L), and resistors (R), resonant automatic equal­izers which equalize an input signal in a frequency domain using a frequency-amplitude characteristic reverse to the frequency-amplitude characteristic of the input signal, and transversal filter type automatic equalizers which equalize in time domains.
  • passive elements such as capacitors (C), induc­tors (L), and resistors (R)
  • resonant automatic equal­izers which equalize an input signal in a frequency domain using a frequency-amplitude characteristic reverse to the frequency-amplitude characteristic of the input signal
  • transversal filter type automatic equalizers which equalize in time domains.
  • Resonant automatic equalizers apply a variable resonator to the input signal subject to selective fading to detect the frequency in the frequency-amplitude characteristic of the input signal and detect the equalization residual in the spectrum of the equalized output signal.
  • an equalized signal is obtained as the output of the variable resonator.
  • An amplitude equalizer using such a resonator is proposed, for example, in Japanese Unexamined Patent Publication (Kokai) No. 60-64515 (published on April 13, 1985).
  • Amplitude equalizers using transversal filters multiply the tap outputs of delay circuits provided with taps by various tap coefficients and sum up the results of the calculations as an output. By varying the tap coefficients in accordance with an error signal obtained by discrimination of the level of the summed output, the error signal is controlled to zero and the output equalized.
  • amplitude equalizers those comprised of constant resistor networks feature a weak resultant frequency-amplitude characteristic and have to be arranged in multi-stage constructions to obtain a powerful amplitude equalization characteristic. This complicates the circuit construction and complicates the design procedure.
  • resonant automatic equalizers can equalize the amplitude-frequency charac­teristic and delay-frequency characteristic when the interference wave is small with respect to the level of the direct wave.
  • the delay-frequency characteristic is inverted, which works with the delay-frequency charac­teristic due to the resonance circuit to conversely deteriorate the delay-frequency characteristic of the output.
  • An amplitude equalizer using a transversal filter can equalize signals subjected to selective fading in the case of an interference wave larger than the level of the direct wave, but the first order component of the amplitude-frequency characteristic in the demodulator is poor, the full equalization capability cannot be exhibited.
  • resonant automatic equalizers and transversal automatic equalizers feature complicated detection circuitry and control circuitry, resulting in not only a tendency to larger circuit sizes but also considerably difficult design procedures.
  • the present invention has as its object the provi­sion of an amplitude equalizer which can equalize the first order slope using a simple construction and has as its further object the provision of an automatic ampli­tude equalizer which can automatically equalize the first order slope with such a simple construction.
  • the present invention features the summing of the outputs of two circuit means having opposite characteristics so as to enable equalization of the first order slope and further the addition of a feedback means to enable automatic amplitude equalization.
  • the above-mentioned circuit means having opposing characteristics are preferably a minimum phase circuit and non-minimum phase circuit.
  • the two circuit means having opposing characteristics use is made, as the two circuit means having opposing characteristics, of generally a positive slope first order amplitude equalizer and a negative slope first order amplitude equalizer.
  • these positive and negative slope first order amplitude equalizers are comprised of the above-mentioned minimum and non-minimum phase circuits.
  • the above-mentioned feedback means use is made of a first order amplitude equalization residual detection circuit.
  • Figure 1 is a schematic block diagram of the amplitude equalizer of the present invention. As shown in the figure, it is constituted by a minimum phase circuit 1 and a non-minimum phase circuit 2 connected in series.
  • the minimum phase circuit 1 emits as an output through a combiner 13 a combination of one of the signals of an input signal S in branched into two ways and a signal consisting of the other signal delayed by a delay element 11 and attenuated by an attenuator 12.
  • the non-minimum phase circuit 2 emits as an output through a combiner 16 a combination of a signal consist­ing of one of the signals of an input signal S ⁇ in branched into two ways, attenuated by an attenuator 14, and a signal consisting of the other signal delayed by a delay element 15. Note that circuits 1 and 2 may be connected in this order or may be connected in a reverse order.
  • Figures 2A and 2B show the equivalent circuit of the minimum phase circuit and the non-minimum phase circuit.
  • the minimum phase circuit 1 as shown in Fig. 2A, branches an input signal into path A and path B, inserts the delay element 11 and attenuator 12 in the signal of path B, and combines the signal of path A and the signal of path B in the combiner 13 for an output.
  • the non-minimum phase circuit 2 as shown in Fig. 2B, branches the input signal into path A and path B, inserts an attenuator in path A and inserts a delay element 15 in path B, and combines the signal of path A and the signal of path B in the combiner 16 for an output.
  • Figure 3 shows the frequency-amplitude characteris­tic (Fig. 3A) and the frequency-delay characteristic (Fig. 3B) when ⁇ and ⁇ in equations (1) and (2) are changed.
  • the delay-frequency character­istic in the case of ⁇ ⁇ 1 in Fig. 2A is reverse from the delay-frequency characteristic in the case of ⁇ > 1 shown in Fig. 2B. Therefore, by connecting in series the circuit of Fig. 2A and the circuit of Fig. 2B, the delay-frequency characteristic in the output is cancelled out and the characteristic becomes flat. Only the amplitude characteristic is added on.
  • ⁇ , ⁇ , and the phases of the paths are set appropriately to obtain the reverse characteristic from the characteristic to be equalized, thus obtaining an amplitude equalizer having the desired equalization characteristic.
  • Figure 4 shows an example of an amplitude equalizer according to the present invention, wherein HYB 1 to HYB 4 are hybrid circuits, DL 1 and DL 2 are delay lines, ATT 1 and ATT 2 are attenuators, and PS 1 and PS 2 are phase shifters.
  • an input signal S in is connected to the input side of the hybrid circuit HYB 1.
  • One of the output sides of the hybrid circuit HYB 1 is connected in series to one of the input sides of the hybrid circuit HYB 2, while the other output side of the hybrid circuit HYB 1 is connected in series through the delay line DL 1 and the attenuator 1 and phase shifter 1 to the other input side of the hybrid circuit HYB 2.
  • the output side of the hybrid circuit HYB 2 is connected to the input side of the hybrid circuit HYB 3.
  • One of the output sides of the hybrid circuit HYB 3 is connected via the attenuator ATT 2 to one of the input sides of the hybrid circuit HYB 4, while the other output side of the hybrid circuit HYB 3 is connected in series via the delay line DL 2 and the phase shifter PS 2 to the other input side of the hybrid circuit HYB 4.
  • the input signal S in is split to the path A and path B in the hybrid circuit HYB 1.
  • the signal of path A is input directly to the hybrid circuit HYB 2, while the signal of path B is delayed by the delay line DL 1, attenuated by the attenuator ATT 1, shifted in phase in the phase shifter PS 1, and then input to the hybrid circuit HYB 2.
  • the hybrid circuit HYB 2 combines the two path signals.
  • the output signal of the hybrid circuit HYB 2 is split to the path C and path D in the hybrid circuit HYB 3.
  • the signal of path C is attenuated by the attenuator ATT 2, then input to the hybrid circuit HYB 4, while the signal of path D is delayed by the delay line DL 2, shifted in phase by the phase shifter PS 2, and then input to the hybrid circuit HYB 4.
  • the hybrid circuit HYB 4 combines the two path signals.
  • the circuit 21 located between the hybrid circuit HYB 1 and the hybrid circuit HYB 2 comprises the minimum phase circuit.
  • Figure 5 shows the frequency character­istics of the minimum phase circuit, Fig. 5A showing the frequency-amplitude characteristic and Fig. 5B showing the delay-frequency characteristic.
  • the interval between two notch frequencies appearing in the frequency characteristics is 1/ ⁇ and is determined by the delay time difference with the path A arising from the delay line DL 1 provided in path B.
  • the position of the notches can be arbitrarily set by changing the phase of the path B. That is, when desiring to change just the position of the notches without changing the interval of the notches, one need only set the phase shift amount of the phase shifter PS 1 to a suitable value.
  • FIG. 6 shows the frequency characteristics of the non-minimum phase circuit 22, Fig. 6A showing the frequency-amplitude characteristic and Fig. 6B the delay-frequency characteristic.
  • Figure 7 shows an example of the design of an amplitude equalizer according to the present invention.
  • the illustrated values are given to the attenuators ATT 1 and ATT 2 and in-phase hybrid circuits are used for the hybrid circuit HYB 1 to hybrid circuit HYB 4
  • the frequency character­istics of the minimum phase circuit 21 and the frequency characteristics of the non-minimum phase circuit 22 becomes as shown by Figs. 7B and C.
  • the frequency characteristics of the circuit of Fig. 7A comprising these connected in series become as shown in Fig. 7D.
  • the abscissas indicate the frequency and the ordinates indicate the delay-frequency charac­teristic P (5 nsec/div) and the frequency-amplitude characteristic Q (5 dB/div).
  • the output of the circuit of Fig. 7A is flat in its delay-­frequency characteristic and augmented in its frequency-­amplitude characteristic.
  • Figure 8 shows an example of the application of the present invention, illustrating the use as a variable first order amplitude equalizer.
  • HYB 11 to HYB 20 indicate hybrid circuits, DL 11 to DL 14 delay lines, ATT 11 to ATT 15 attenuators, PS 11 to PS 13 phase shifters, and VATT a variable attenuator.
  • the portions located between the hybrid circuit HYB 12 and HYB 13 and between the hybrid circuit HYB 16 and HYB 17 constitute the minimum phase circuits 31 and 32, while the portions located between the hybrid circuit HYB 14 and HYB 15 and the hybrid circuit HYB 18 and HYB 19 constitute the non-minimum phase circuits 33 and 34.
  • the circuit of Fig. 8 comprises amplitude equalizers shown in Fig.
  • the interval between the notch frequency of the path I comprised of the minimum phase circuit 31 and the non-minimum phase circuit 33 and the notch of the path II comprised of the minimum phase circuit 32 and the non-minimum phase circuit 34 is selected to be 1/2 ⁇ by the phase-shifters PS 12 and PS 13 within the path I, as shown by Fig. 9.
  • a certain range X centered on the intersecting frequency F0 of the two characteris­tics is used as the transmission band. Therefore, there is a relative phase difference of 180° between the signal of path I and the signal of path II.
  • variable attenuator VATT may be of any type so long as it can be varied in its attenuation level. Also, it may be inserted into either the path I or path II or may be inserted in both paths.
  • Figures 10A to F and 11A to C show specific examples of the characteristics of the variable first order amplitude equalizer of Fig. 8. These show the delay-­frequency characteristic P (ordinate, 5 nsec/div) and the frequency-amplitude characteristic Q (ordinate, 5dB/div) of various parts, with the frequency as the abscissa, when the notch frequencies of the minimum phase circuits 31 and 32 in the circuit of Fig. 8 are set to 47 MHz and 93 MHz, respectively, and the notch frequencies of the non-minimum phase circuits 33 and 34 are made 47 MHz and 93MHz, respectively.
  • Figure 10A shows the characteristic of the minimum phase circuit 31, Fig. 10D the characteristic of the minimum phase cir­cuit 32, Fig.
  • Fig. 10B the characteristic of the non-minimum phase circuit 33
  • Fig. 10E the characteristic of the non-minimum phase circuit 34
  • Fig. 10C the characteristic of the path I comprised of the minimum phase circuit 31 and the non-minimum phase circuit 33 connected in series
  • Fig. 10F the characteristic of the path II comprised of the minimum phase circuit 32 and the non-minimum phase circuit 34 connected in series
  • Figs. 11A, 11B, and 11C the characteristics of variable first order amplitude equalizer of Fig. 8 as a whole with path I and path II connected in parallel.
  • the characteristics of the path I are a combination of the characteristics of the minimum phase circuit and the non-minimum phase cir­cuit 33.
  • the delay-frequency characteristic is flat, and the frequency-amplitude characteristic is augmented.
  • the characteristics of the path II are a combination of the characteristics of the minimum phase circuit 32 and the non-minimum phase circuit 34, with the delay-frequency characteristic being flat and the frequency-amplitude characteristic being augmented.
  • a combination of the outputs of the two paths is obtained as the output of the hybrid circuit HYB 20. At this time, three types of characteristics are obtained depending on the magnitude of the attenuation by the variable attenuator VATT.
  • Figures 11A and 11C show the characteristics of the overall circuit of Fig. 8 in the case of the attenuation of the variable attenuator VATT being smaller and larger than the attenuation of the attenuator ATT 15.
  • the delay-frequency characteristics are flat, while the frequency-amplitude characteristics become a negative first order slope and a positive first order slope, respectively.
  • Figure 11B shows the characteristics of the overall circuit of Fig. 8 in the case where the attenuation of the variable attenuator VATT and the attenuation of the attenuator ATT 15 are equal.
  • Both the delay-frequency characteristic and the frequency-­amplitude characteristic are flat.
  • the center frequency f0 of the band in this case is the center frequency of the 47 MHz notch frequency of the path I and the 93 MHz notch frequency of the path II, that is, 70 MHz.
  • FIG. 12 is a view of the constitution of an automatic amplitude equalizer based on the circuit of Fig. 8.
  • a feedback means 41 is introduced into the circuit of Fig. 8 so as to change the amount of attenuation of the variable attenuator VATT in accordance with the equalization residual in the output signal.
  • Figure 13 is a view of a specific constitution of the automatic amplitude equalizer of Fig. 12.
  • a variable amplitude equalization circuit corresponding to the circuit of Fig. 8 is indicated by 51 and is shown generally. It is specifically constituted by a negative slope first order amplitude equalizer 56 (corresponding to 31 and 33 in Fig. 12), a positive slope first order amplitude equalizer 55 (corresponding to 32 and 34 in Fig. 12), a variable attenuator 57 (corresponding to VATT in Fig. 12), and a combining circuit 58 (corre­sponding to HYB 20 in Fig. 12).
  • the feedback means 41 of Fig. 12 comprises an automatic gain control (AGC) amplifier 52, a detection circuit 53, and a control circuit 54.
  • AGC automatic gain control
  • the circuit is comprised of an automatic gain control amplifier 52 for making constant the output signal of a variable amplitude equalization circuit 51, a detection circuit 53 for detecting the first order amplitude equalization residual of the frequency-ampli­tude characteristic of the output signal of the automatic gain control amplifier 52 using a narrow band filter, detector, etc., and a control circuit 54 for controlling the variable amplitude equalization circuit 51 based on the detected output signal of the detection circuit 53.
  • the variable amplitude equalization circuit 51 has a variable attenuator 57 for adjusting the output signal level of either one of the positive slope first order amplitude equalizer 55 and the negative slope first order amplitude equalizer 56.
  • the variable attenuator 57 is controlled by the above-mentioned control circuit 54. Signals are combined by a combining circuit 58 for output.
  • the automatic gain control amplifier 52 amplifies the signal to a certain level and outputs the result.
  • the first order amplitude equalization residual is detected by the detection circuit 53, and, based on the detected output signal, the variable attenuator 57 of the variable amplitude equalization circuit 51 is controlled by the control circuit 54.
  • the variable amplitude equalization circuit 51 the output signal levels of the amplitude equalizers 55 and 56 of the positive slope and negative slope are adjusted and the vector-added, so when the two have opposite frequency-­amplitude characteristics, the vector-addition results in a flat frequency-amplitude characteristic. If the amount of attenuation of the variable attenuator 57 is made larger, the frequency-amplitude characteristic of the other output signal becomes the characteristic of the combined output signal.
  • variable attenuator 57 for a minimum first order amplitude residual, the first order component of the frequency-amplitude characteristic due to the fading can be equalized without deterioration of the group delay-­frequency characteristic. Further, the control circuitry controls a single variable attenuator 57 through detec­tion of the first order component, so becomes simple in construction.
  • FIG. 14 is a somewhat more concrete view of the automatic amplitude equalizer of Fig. 13.
  • 61 indicates a variable amplitude equalization circuit
  • 62 an automatic gain control amplifier
  • 63 a detection circuit
  • 64 a control circuit
  • 66 a positive slope first order ampli­tude equalizer
  • 67 a negative slope first order amplitude equalizer
  • 68 a fixed attenuator
  • 69 a variable attenua­tor
  • 71 and 72 narrow band filters and 73 and 74 detectors.
  • the signal received through a digital radio trans­mission line is converted in frequency to become an intermediate frequency (IF) signal and input to the variable amplitude equalization circuit 61.
  • the input signal is branched into two by the hybrid circuit 65 and supplied to the positive slope first order amplitude equalizer 66 and the negative slope first order amplitude equalizer 67.
  • the output signal of the positive slope first order amplitude equalizer 66 is applied to the fixed attenuator 68 and the output signal of the negative slope first order amplitude equalizer 67 is applied to the variable attenuator 69.
  • the output signals of the fixed attenuator 68 and the variable attenuator 69 are applied to the hybrid circuit 70 and vector added.
  • variable attenuator 69 for example, PIN diode
  • control circuit 64 by con­trolling the variable attenuator 69 (for example, PIN diode) by the control circuit 64, it is possible to obtain a desired negative first order slope character­istic as the combined output characteristic, so it is possible to compensate for the first order component of the frequency-amplitude characteristic of the input signal.
  • the output signal of the variable amplitude equal­ization circuit 61 is amplified so as to become fixed in level by the automatic gain control amplifier 62.
  • the first order amplitude equalization residual is detected by the detection circuit 63 from the output signal of the automatic gain control amplifier 62.
  • different frequency components are extracted by the band filters 71 and 72, detected by the detectors 73 and 74, and supplied to the control cir­cuit 64.
  • the levels of the output signals detected by the detectors 73 and 74 are compared and the variable attenuator 69 is controlled in accordance with the first order amplitude equalization residual. For example, when the detected output signal levels are equal, the amount of attenuation of the variable attenuator 19 is controlled to be the same as the attenuation of the fixed attenuator 68.
  • Vector addition of the characteristics of the positive slope first order amplitude equalizer 66 and the negative slope first order amplitude equalizer 67 gives a flat frequency-amplitude characteristic.
  • the first order amplitude equalization residual When the level (E H ) of the detected output signal having the higher frequency is greater than the level (E L ) of the output signal having the lower frequency, the first order amplitude equalization residual exhibits a positive slope first order amplitude characteristic, so control is effected to reduce the attenuation of the variable attenuator 69.
  • the variable amplitude equal­ization circuit 61 is made to exhibit a negative slope frequency-amplitude characteristic, and it is possible to equalize the frequency-amplitude characteristic resulting from the fading.
  • the output signal of the negative slope first order amplitude equalizer 67 was added to the variable attenuator 69, but it is also possible to structure things so that the output signal of the positive slope first order amplitude equalizer 66 is applied to the variable attenuator 69 and the output signal of the negative slope first order amplitude equalizer 67 is applied to the fixed attenua­tor 68. Further, it is possible to make both the two attenuators (68 and 69) variable. Still further, while it is advantageous to use equalizing circuits of the structure of Fig.
  • FIG. 4 shows another embodiment of the variable amplitude equalization circuit of Fig. 13, wherein general L-R-C type circuits are used for the equalizers 55 and 56.
  • Figures 16 shows an example of the control circuit of Fig. 14.
  • the low frequency (L) side output E L and high frequency (H) side output E H output from the detection circuit 63 are input to a subtractor 81 and the level difference E L - E H of the two is calculated. If E L - E H > 0, a negative slope characteristic appears. If E L - E H ⁇ 0, a positive slope characteristic appears.
  • the level difference E L - E H is amplified by an amplifier 82, then becomes the control input of the variable attenuator 69 (Fig. 14). If the attenuator 68 (Fig.
  • the 14) is also comprised of a variable attenuator, the polarity of the above-mentioned level difference is inverted by an inverter (INV) 83 to give -(E L - E H ). This is used as the control input for the attenuator 68.
  • the adders 84 and 85 add an offset DC voltage to E L - E H and -(E L - E H ). This sets the gain of the attenuator to the optimum reference value. It is possible to perform equalization by just the gain control of the attenua­tor 68, but if the gains of both the attenuators 68 and 69 are controlled, it is possible to perform the wide range equalization.
  • an amplitude equalizer is realized which can flatten the delay-frequency characteristic through addition of the outputs of two circuit means having opposite characteristics and can produce a strong frequency-amplitude characteristic. If such equalizer amplitudes are connected in parallel, a variable ampli­tude equalizer can be realized. In this case, level adjustment is performed on the positive slope and/or negative slope first order amplitude equalizer side. If this level adjustment is performed in accordance with the magnitude of the equalization residual apperaring in the output signals, an automatic amplitude equalizer can be realized.
  • Each of the above-mentioned amplitude equalizer, the variable amplitude equalizer, and the automatic amplitude equalizer can be realized with a simple construction.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Filters And Equalizers (AREA)
EP87111977A 1986-08-18 1987-08-18 Amplitudentzerrer Expired - Lifetime EP0257526B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP61191636A JPH06101696B2 (ja) 1986-08-18 1986-08-18 自動振幅等化器
JP191636/86 1986-08-18
JP307470/86 1986-12-22
JP30747086A JPS63158921A (ja) 1986-12-22 1986-12-22 振幅等化器

Publications (3)

Publication Number Publication Date
EP0257526A2 true EP0257526A2 (de) 1988-03-02
EP0257526A3 EP0257526A3 (en) 1989-11-15
EP0257526B1 EP0257526B1 (de) 1993-12-29

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Application Number Title Priority Date Filing Date
EP87111977A Expired - Lifetime EP0257526B1 (de) 1986-08-18 1987-08-18 Amplitudentzerrer

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US (1) US4870658A (de)
EP (1) EP0257526B1 (de)
CA (1) CA1275710C (de)
DE (1) DE3788603T2 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0427951A2 (de) * 1989-10-27 1991-05-22 ALCATEL ITALIA Società per Azioni Einrichtung zur Erzeugung von Schaltkriterien und zur adaptiven Entzerrung von Datensprektren
GB2293948A (en) * 1994-09-27 1996-04-10 Fujitsu Ltd Digitally controlled automatic amplitude equalizers
GB2330743A (en) * 1994-09-27 1999-04-28 Fujitsu Ltd Automatic amplitude equalizer

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US5355103A (en) * 1990-06-29 1994-10-11 American Nucleonics Corporation Fast settling, wide dynamic range vector modulator
US5506549A (en) * 1994-11-14 1996-04-09 Dsc Communications Corporation Cable equalizer
US6362440B1 (en) * 1998-03-27 2002-03-26 International Business Machines Corporation Flexibly interfaceable portable computing device
US7042936B2 (en) * 2002-04-18 2006-05-09 The Boeing Company Dynamic amplitude tilt equalizer
EP2820487A4 (de) 2012-02-29 2016-04-06 Micreo Ltd Formungsmittel für eine elektronische verstärkung und verfahren zum speichern von parametern
US9484878B2 (en) 2014-02-18 2016-11-01 Viasat, Inc. Equalization of frequency-dependent gain
CN111224907A (zh) * 2019-11-21 2020-06-02 中电科仪器仪表有限公司 一种大带宽宽频带变频链路幅度均衡方法

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US4258340A (en) * 1978-04-12 1981-03-24 Nippon Electric Co., Ltd. Amplitude equalizer
EP0048646A1 (de) * 1980-09-12 1982-03-31 Thomson-Csf Einrichtung zur Korrektur der Amplitudenverzerrungen von Funksignalen und eine solche Einrichtung enthaltender Empfänger
JPS57207440A (en) * 1981-06-16 1982-12-20 Fujitsu Ltd Variable circuit for amplitude characteristic

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US4258340A (en) * 1978-04-12 1981-03-24 Nippon Electric Co., Ltd. Amplitude equalizer
EP0048646A1 (de) * 1980-09-12 1982-03-31 Thomson-Csf Einrichtung zur Korrektur der Amplitudenverzerrungen von Funksignalen und eine solche Einrichtung enthaltender Empfänger
JPS57207440A (en) * 1981-06-16 1982-12-20 Fujitsu Ltd Variable circuit for amplitude characteristic

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IEEE International Conference on Communications ICC'81, Denver, June 14-18, 1981, Vol. 1, pages 13.6.1 - 13.6.9; IEEE, New York, US, E. JOHNSON: "An adaptive of equalizer for digital transmission", pages 13.6.2 - 13.6.3, section: "Slope equalizer"; figure 5. *
PATENT ABSTRACTS OF JAPAN, Vol. 7, No. 62 (E-164)(1207), March 15, 1983; & JP,A,57 207 440 (FUJITSU K.K.) 20-12-1982, Abstract. *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0427951A2 (de) * 1989-10-27 1991-05-22 ALCATEL ITALIA Società per Azioni Einrichtung zur Erzeugung von Schaltkriterien und zur adaptiven Entzerrung von Datensprektren
EP0427951A3 (en) * 1989-10-27 1992-09-02 Telettra Telefonia Elettronica E Radio S.P.A. System to generate switching criteria and equalize adaptively in data spectrum
GB2293948A (en) * 1994-09-27 1996-04-10 Fujitsu Ltd Digitally controlled automatic amplitude equalizers
GB2330743A (en) * 1994-09-27 1999-04-28 Fujitsu Ltd Automatic amplitude equalizer
GB2293948B (en) * 1994-09-27 1999-05-19 Fujitsu Ltd Automatic amplitude equalizer
GB2330743B (en) * 1994-09-27 1999-06-16 Fujitsu Ltd Automatic amplitude equalizer
US5978415A (en) * 1994-09-27 1999-11-02 Fujitsu Limited Automatic amplitude equalizer

Also Published As

Publication number Publication date
EP0257526A3 (en) 1989-11-15
EP0257526B1 (de) 1993-12-29
DE3788603T2 (de) 1994-06-09
DE3788603D1 (de) 1994-02-10
US4870658A (en) 1989-09-26
CA1275710C (en) 1990-10-30

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